ICAPP: A process planning system for the CIM environment

ICAPP: A process planning system for the CIM environment

ICAPP: A process planning system for the CIM environment MUKASA E SSEMAKULA Abstract: This paper describes an approach to the integration of process ...

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ICAPP: A process planning system for the CIM environment MUKASA E SSEMAKULA

Abstract: This paper describes an approach to the integration of process planning with computer aided design. The link is established through IGES, which is used to transfer the geometric data from the CA D system to the process planning system. The process planning system can subsequently use this data in generating a detailed process plan as well as an NC part program for the manufacture of the part. Keywords: IGES, computer integrated computer aided process planning

manufacturing,

oday's industrial climate is one of intense competition, with great emphasis being placed on reducing costs and improving productivity, product quality as well as reliability. To achieve these goals, manufacturers have had to adopt radical new production techniques. The use of computers in various fields such as design, control and manufacture has been of particular importance. Experience in the use of various computer-based systems in industry has shown that while each can individually benefit the production process, these gains would be enhanced if the systems were integrated. There are many functions in which at least some of the required information is common. In such cases, it makes sense to provide means by which these functions can share the common information. Computer Integrated Manufacturing (CIM) is a major long-term research objective including elements such as robotics, process planning, computer aided design and scheduling, among others. The goal of this paper is to demonstrate how the development of Computer Aided Process Planning (CAPP) systems can play a major role in the development of Computer Integrated Manufacturing (CIM). This concept has been successfully implemented in a CAPP system for prismatic parts. In this paper, work is described that has been undertaken to build robust interfaces between a generative process planning system (ICAPP), a stateof-the-art CAD system, and an automated flexible

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Wayne State University, Division of Engineering Technology, Detroit, M1 48202, USA

manufacturing facility. An example to illustrate the operation of the integrated system is also presented.

Computer aided process planning Process planning is defined as the task of translating part design specifications into manufacturing instructions required to convert a part from rough state to a finish state I. Traditionally, it is performed manually by highly skilled workers who possess in-depth knowledge of the manufacturing processes involved, and the capabilities of the machine tools available. On the basis of their experience, they are expected to develop a detailed process plan to be used in manufacturing the part. This involves selecting the appropriate machine tools, jigs and fixtures; determining the appropriate machining operations and associated cutting conditions, as well as calculating the cutting times and non-cutting times. A detailed knowledge of the particular manufacturing environment is necessary because it imposes constraints on available alternatives. The result is a detailed process plan which includes machine tools to be used, sequence of operations, cutting conditions, as well as tools and fixtures. This activity is very labour-intensive, and often becomes tedious when dealing with a large number of process plans, and revisions to those plans. Rather than carry out an exhaustive analysis and arrive at optimal values, which would be too time consuming, process planners all too often play safe by using conservative values. This has the unfortunate side effect that if several process planners with different backgrounds are given the same part to plan, they will probably come up with different plans. Even more significantly, the same planner, if required to generate a plan for the same part on different occasions, will probably come up with inconsistent results 2. Consequently, the speed and consistency brought about by the computer has long been sought in process planning. Another factor is the lack of qualified and experienced process planners. Typically, process planners in the US have significant experience in a machine shop and are over 40 years old. It is estimated that the US industry requires up to

0951-5240/93/040235-09 (~) 1993 Butterworth-Heinemann Ltd Vol 6 No 4 November 1993

235

ICAPP: A process planning system for the CIM environment 300,000 process planners, and less than 200,000 are currently available 3. Thus, another advantage of the use of computers in process planning is that it can reduce the skill required of the planner. Computer Aided Process Planning (CAPP) can be implemented at two levels:

• Stand-alone systems As a stand-alone system, CAPP can generate process plans faster and with better consistency than human process planners. CAPP systems, for example, can calculate optimum cutting conditions based on varying criteria such as minimizing costs, or minimizing machining time. With the use of artificial intelligence (AI) techniques, they can incorporate manufacturing rules to select and sequence the appropriate processes to complete the process plan. Computers can thus free expert process planners to work on cases which fall outside the scope of the CAPP system. • Within Computer Integrated Manufacturing CAPP's function is to transform the part design into manufacturing instructions. This requires the use of design information such as the part geometry. Based on this, the system calculates the detailed data required for manufacturing as outlined above. Thus CAPP is an ideal candidate to fully integrate CAD and CAM (see Figure 1). Present day CAD/CAM systems are capable of generating geometrical data to support machining, but will still not yield NC part programs without extensive interaction with the user. Also, CAD/CAM systems are not sufficient to integrate with the other building blocks of CIM because they cannot generate the necessary timing and control information needed for CIM integration. The CAPP link will help provide the timing information required for planning and scheduling by calculating machining times. Thus, in addition to the automatic generation of the relevant technical data, such as cutting conditions and manufacturing sequences, CAPP could also provide timing information to MRP II systems, as suggested in a proposed CIM architecture 4 and illustrated in Figure 1.

Implementing C A P P There are two major approaches to CAPP currently found in the literature. The first approach is called a variant approach and is based on the concept of Group Technology (GT). For a given family of parts, the detailed process plan for a representative member of the family is developed with the help of an experienced process planner. Plans for several part families are similarly developed and stored on the system's database. The major characteristics of the new part are used to retrieve a previous process plan for a part in the same family which has similar features. The retrieved process plan can be modified easily to match the new part. Developing a new process plan thus consists of retrieving the standard process plan for a family of

236

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Figure 1. CAPP's role in proposed CIM architecture parts and tailoring it to the characteristics of a specific part. Examples of such systems include MIPLAN 5 and DCLASS 6, which have been implemented in the industry. The second approach is generative, and creates a new process plan for each part. Generative CAPP systems use their own internal logic to derive a new process plan based on the characteristics of the part and the machine it is to be manufactured on. AUTAP 7, APPAS 8 and SIPS ~ are such systems. The advantage of variant systems is that they can be implemented in the industry fairly easily, however they do not truly solve the problem of automating the process planning function since they still rely on human process planners to develop representative process plans and review them for possible new applications. The generative approach can create new process plans for parts which fall within its scope. Therefore a new, complete and up to date process plan is created for every new part with little human intervention. It is estimated that generative process planning systems have the potential to reduce the planning labour costs by up to 60% 10. Also, because it requires detailed part characteristics input, it can serve as the basis for integration with CAD and various CAM modules. Most of the CAPP systems available today are of the stand-alone type. There are few systems described in the literature which generate NC part programs from CAPP. Eversheim describes one such system, AUTAPNC 11, for rotational parts and sheet metal stamped parts. The Automated Manufacturing Research Facility (AMRF) at the National Institute of Standards and Technology (NIST) used this approach to generate the part programs for a particular milling machine from a process planning system integrated with a design and NC code generation package 12. The system described here is based on the ICAPP generative process planning program for prismatic parts.

Development of the ICAPP system ICAPP is an interactive feature oriented computer aided process system developed for prismatic parts 13. It is based on the notion of features and can handle the following eight features (and associated machining operations):

Computer Integrated Manufacturing Systems

M E SSEMAKULA • • • • • • • •

face (face milling) side (milling) slot (milling) pocket (milling) holes (drilling, boring, reaming) thread (tapping) counterbored holes (counterboring) countersunk holes (countersinking).

In the original version, the user was required to answer a series of dependent questions on the geometry and other manufacturing details of the machinable features. On the basis of this input, the system generated an operator readable process plan, detailing the required machine tools, operation times, feeds, speeds, depth of cut, etc. The first extension to ICAPP was to include an interactive mode for NC data generation to produce COMPACT II part programs I~. This required additional geometric data to that available for straight forward process planning; but even at this level, there was no direct link established to transfer geometric data directly to ICAPP from CAD. Consequently, work aimed at automated transfer of product definition data from the design system to the process planning system was initiated. One of the main problems arising in this data transfer is the compatibility of present day systems with regards to CAD data. Every system has a unique way of representing the geometric data of the part within the CAD database. This problem has been recognized for some time, and as a result work has been undertaken to develop standard formats that would provide a viable means of communication between different CAD systems. Several formats have been developed as a result of such work, the most well known ones being IGES I-~, SET 16 and VDA-FS w. Of these, IGES is the predominant standard among CAD/CAM users and was used for the work described here. More recently, the PDES/STEP standard has been proposed, although this is so new that no commercially available CAD systems have implemented it yet. We have started doing some work in developing an interface to the ICAPP system that would accept PDES input data, and this is discussed elsewhere TM.

Planning with ICAPP For each feature to be produced, the system checks the capability of the machine tool in use by searching through a database of available machines. It then selects the best cutting conditions based on the power of the machine tool, the material of the workpiece and the cutting tool which the system has selected. Based on surface finish requirement, the system generates the appropriate rough machining and finish machining operations. It should be noted that the system handles each feature discretely. This means that the operations generated at this stage are locally optimal, relative to each feature. Once all the features have been described,

Vol 6 No 4 November 1993

the system selects the best sequence for manufacturing the part based on manufacturing rules tg. In sequencing the operations, the system takes into account any feature interactions, operation dependencies and precedence relationships. At this stage, the system has generated a fully detailed and sequenced process plan for the part, including: operation type, feed, cutting speed, RPM, depth of cut, width of cut, tooling information, number of passes and machine to use. The program is then ready to generate part programs if the user specified this option. The part program can be in either APT or COMPACT II.

Interfacing ICAPP with CIM modules

IGES overview ICAPP has been interfaced with CAD modules through use of IGES. IGES covers a wide range of application areas including electrical, plant design, as well as mechanical applications. IGES thus provides a standard format by which the user can transfer the data from one CAD system to another. A standard format such as IGES requires the use of two processors or translators. The preprocessor takes as input CAD data as described in the system-specific format for the originating system, and converts this into the IGES format. The postprocessor converts data in the IGES format into the system-specific format for the receiving system, and the resulting file can be used to regenerate the original CAD model. IGES has established particular information structures or entities to be used for digital representation and communication of product definition data. The data is represented as a structured file in a specific format which enables exchange of product definitions between various CAD systems. The product is described in terms of geometric and non-geometric information. The geometric information is the actual drawing data consisting of various entities that make up a feature or a part. The non-geometric information consists of annotations, definitions and organizational data. The fundamental unit of information in the file is the entity. Geometric entities represent the definition of the physical shape and include points, curves, surfaces and relations, which are collections of similarly structured entities. Non-geometric entities provide a viewing perspective in which a planar drawing may be composed and also provide annotation and dimensioning appropriate to the drawing. These non-geometric entities include view, drawing, dimensions, text, notation, witness lines and leaders. In representing geometry, the edge representation method is implemented in IGES. It should be noted that IGES was primarily developed to serve the purpose of transferring drawing data between CAD systems. Thus IGES was designed to address data that is required in generating a part drawing, mainly geometry. IGES has been remarkably successful in this task but at the same time it has some significant limitations. Once the part data has been

237

ICAPP: A process planning system for the CIM environment transferred to another CAD system, the data can be utilized by other applications including manufacturing, inspection and assembly, among others. For these applications, however, additional information such as geometrical and dimensional tolerances, surface finish, and fit specification for mating parts, is required. This information, however, is not available in IGES, and therefore cannot serve the purpose of complete product definition. This indeed is the reason for developing the new and emerging PDES/STEP standard mentioned above. Within the limitations of IGES, however, we have endeavoured to develop a system that can link the CAD and process planning functions by at least supplying the geometry information required for the latter directly from the former. Any additional information that is required such as tolerances can be entered subsequently on an interactive basis. A standard IGES file consists of six sections. Each section is identified in the IGES file itself by a corresponding code printed in the output file, as shown in Table 1. IGES data can be represented in either ASCII or binary format. Binary format uses a byte oriented file structure, and is suitable for the transfer of large files. For this work, relatively simple features were being handled and the IGES files generated for their description were not large, thus it was adequate to use the ASCII format. In the ASCII format, each line in the IGES file contains 80 characters. The code identifying the section is printed in column 73 of each line. Columns 74-80 show the sequence number of each line within the section. The sequence number is a seven digit string starting from 0000001, increasing sequentially according to the number of lines in the section. Implementing I G E S in I C A P P For geometry data transfer between CAD and process planning, the information that is required from the IGES file is the parametric data defining the geometry of the features on the component. Our work concentrated on extracting this information and interpreting it properly for use within the ICAPP process planning system. ICAPP handles fairly simple features such as holes, slots and pockets. For these types of features, the only geometric entities required to define each feature are lines, arcs and circles. Thus these are the

only entities that need to be transferred from the CAD system to ICAPP. The purpose, therefore, was to extract all geometrical entities of the above forms from the IGES file, group together all those elements constituting features, and transfer this features data into the ICAPP system for subsequent use in process planning. Typical entries in the parameter data section of an IGES file to describe line, arc and circular entities, respectively, are shown in Table 2. In the parameter data shown in Table 2, code 110 in the first column indicates that the data corresponds to a line entity whereas code 100 indicates a circular entity. Data entries are separated by commas, and the end of parameter data is indicated by a semi-colon. For a line entity, the parameter data consists of a start point (xl, Yl, zl) and an end point (x2, Y2, Z2)' For a circular entity, the data consists of the z coordinate location; location of the centre of the arc or circle (x0, Yo), start point of the arc (xz, Yl) and the end point of the arc (x2, Y2). A circle can be distinguished from an arc because its start and end points will coincide. A user defined tolerance value is applied here in determining coincidence of points to account for the round-off errors inherent in a digital computer when dealing with real numbers. The non-geometric attributes such as notes, labels, colour and text associated with the geometric entity are present in the directory section of the IGES file, and are indicated by means of pointers.

Graphics interface A graphics interface was developed and implemented into ICAPP, which has the capability of reading the datafile described above and, using the PLOTI0 library of graphics routines, reproducing the part drawing within the ICAPP system. This capability was implemented for the simple transfer of geometry data required to describe manufacturing features to the process planning system. An earlier interface was developed at UMIST 2°. However, the UMIST interface regenerated all the CAD drawing data in the received IGES file, including dimensions and text. The complete part drawing was thus available on screen, and the necessary geometry data was interactively input into the process planning system by reading textual information off the regenerated drawing on the screen. In the work presented here, the principle aims were achieving complete system integration and minimizing manual data entry, with a view to making the process of data input faster, and at the same time reduce the

Table 1. IGES file structure and codes

Section

Code

Flag section (optional) Start section Global section Directory entry section Parameter data section Terminate section

B/C S G D P T

238

Table 2. Sample IGES parameter data for geometric entities

110,84.16,69.3,0. ,84.16,15.08,0.; 100,- 12. ,25. ,30. ,54. ,30. ,25. ,50.; 100,0. ,40. ,40. ,55. ,40. ,55. ,40.;

00000054P0000016 00000040P0000021 00000039P0000022

Computer Integrated Manufacturing Systems

M E SSEMAKULA likelihood of errors associated with manual systems. The final drawing reproduced within ICAPP with this approach did not need to include textual or dimensional information. The required geometry data was obtained directly from the input IGES file. This is done by indicating the feature of interest during the process planning phase. As the ICAPP system progresses through the various process planning stages, the user is prompted to indicate the relevant feature on the part drawing whenever there is any geometric information required for process planning. The cross-hair cursor is presented, which the user can then move to the appropriate entity on the feature and make a selection. The geometry data associated with the selected entity is retrieved from the database and stored in a special array for later use in the generation of the process plan. This eliminates possible human errors in manually entering numerical data for a large number of entities constituting the part. Features are processed iteratively until all the features on the component have been processed. When this is done, all the geometry data stored in the special array is retrieved to extract feature information such as diameter and depth of hole; perimeter and depth of pocket; length, width and depth of slot, etc. The system then generates an optimal process plan using its basic process planning modules. The system can then generate NC part programs in either COMPACT II or APT (as described below). Since generation of part programs requires extra geometry information over and above that needed for process planning, this can also be entered here using the same approach. As an example, consider the flow of data during the processing of a simple hole. The geometric data required for hole processing is the hole diameter, and the depth of the hole. In addition, the exact location of the hole on the workpiece is required to generate the NC part program. During process planning of a particular component, the part number is used to retrieve the IGES data for the component. When the process planning system requires geometric data, an isometric view of the component is regenerated on the screen and geometric entities can be indicated directly on the screen. For the hole making operation, the system asks the user to indicate the hole to be planned by making a cursor selection. When the selection is made, the system automatically retrieves all the geometric data associated with the selected hole, by scanning the geometric data file for all parametric data defining the entity selected on the screen (as well as all the other entities grouped with the selected entity to constitute the hole feature). The entities so retrieved are highlighted on the screen, and the user is asked to confirm if these represent the feature desired. Once the selection is verified, the required geometric data is extracted. The diameter of the hole would be calculated from the diameter of either of the circular entities associated with the hole, and the depth of the hole would correspond to the length of the linear entities. The location of the hole would be determined from the

Vol 6 No 4 November 1993

centre of one of the circular entities associated with the feature. This data is then automatically transferred to the process planning module to carry out detailed process planning and generation of NC part programs. A similar approach is used for all the other features handled by ICAPP. Geometry data is specified by making cursor selections on the screen. Selected entities are highlighted for verification, and on confirmation the associated geometry data is transferred to the process planning modules for detailed process planning to continue. For more details on the technique used, the reader is referred to Ssemakula and Gill23.

NC part programming interface An NC part program can take many different forms depending on which level it is meant to be written for. At the machine controller level, it is a set of M and G codes which control the various functions of the machine such as spindle location, cutting conditions, coolant, etc. The advantage of using these codes is that the simpler ones have been standardized and make the system machine independent. However, most NC machines have their own set of codes for advanced functions. These codes invoke standard routines, or canned cycles, which are optimum for that machine. It is therefore more advantageous to use higher level languages which are then postprocessed for a particular machine tool and controller combination, and will make use of the particular advanced features built in the machine tool. The ICAPP system can generate part programs in both APT and COMPACT II. The distribution of intelligence in ICAPP is such that it will take full advantage of the advanced features of both systems and use its own logic when required. The structure of an NC part program in both of these languages consists of: • • • •

initialization geometry definitions tooling and machining instructions program termination.

Accordingly, ICAPP generates part program statements in the same order (Figure 2).

NC statement generation On the basis of the geometric data derived from the IGES input file, and the process plan generated by the system, ICAPP can generate a complete NC part program that can be used to produce the component. The system described here provides a means of automatically generating a part program for each machine tool necessary to manufacture the part. Based on the machine tool code, the system retrieves the name of the postprocessor for APT part programs, and the name of the link for COMPACT II part programs. The setup statements are issued using information stored in the machine tool database as well as specific

Z39

ICAPP: A process planning system for the CIM environment

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The output of the process plan includes a list of tools to be used on the machine tool. Those same tool numbers are used to specify the number of the tool to load, to be able to machine a given feature. If a change of face is detected during the scanning of the process plan, the tool change statement will contain an optional stop to enable the operator to change the orientation of the workpiece for non 5-axis machines. Once the tool is loaded, the appropriate cutting statements are issued. To do so, the previously generated process plan is scanned and machining operations are recognized. For each operation, the associated geometry statements are retrieved using the drawing code and are used to guide the tool in machining. Different algorithms are used for machining different types of features. The strategy employed is closely linked to the concepts used in the process planning function; for example, the process plan will generally specify three passes for a slot (one in the middle, and one on each side) if it cannot use only one. This is respected in the machining statements and appropriate stock value are calculated to perform this task. If side finish of the slot is required, the tool will stay in the slot and machine the sides again using the finish cutting conditions calulated by the system. Once a feature is completed, the tool is retracted from the depth of the feature and the system proceeds to the next operation. The part program is terminated once all the machining operations have been scanned. The tool is retracted to the tool change position and a termination statement is appended. If more than one machine tool is required to make the component, then an important restriction is imposed by the system. The restriction is that once the part leaves a given machine, it does not return to that machine for any subsequent operation. This is necessary because when the component leaves a machine, its setup changes. Thus a new setup and a new part program would be required if the part returns to the machine, but this system generates only one part program for each machine during a given run.

information on where that part will be positioned in reference to the machine. The system then issues the geometry definitions by scanning through a database which contains definitions of the geometric elements associated with each feature. The geometric elements considered for holes, are randomly positioned points, as well as linear and circular patterns of points, where each point represents the centre of a hole. For milling operations, the contours are defined using lines and circles. These definitions are related to the machinable features through a drawing code for each feature. The proper format is chosen and various subroutines account for the different types of geometry definitions. Once the geometry definitions are issued, the system scans the process plan for the part and extracts any required information to generatethe tool changing and machining statements.

240

Example A simple example to illustrate the capabilities of the system was processed and is presented here. Figure 3 shows the drawing of the component, as well as its process plan as generated by ICAPP. The geometry was input as described above, and on the basis of this the process plan was generated. In addition, part programs to machine the component were generated in both APT and COMPACT II, and these are shown in Figure 4. These part programs can be processed using standard postprocessing routines to generate M and G codes for the machine. We have developed custom postprocessors to generate codes for the machines in the flexible manufacturing cell at this university. The resulting part program can be checked using an NC part verification function, before downloading to the shopfloor for execution. Using this system, a complete part program using optimal cutting conditions and tools, can

Computer Integrated Manufacturing Systems

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7.1

! INSPECTION l

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TOTAL SET-UP TII4E

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1.00 WIN

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TOTAL MACHINING TIHE PEA CONPONEHT = o.

0.81 HIN

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TOTAL HIHDLINO TIME PEA COI,~OIiENT =

..--

6 . 2 6 HIN

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TOTAL TII4E FOH HATCH =

8.08 MIX

ksuwH

: MM/RPM FOR HOLE MAKIIIG OPERATIONS MM/Mlll FOR MILLING

II~S

- M/SEC = 1414 - 144

E~PI~ WIDTH

Figure 3. Sample part and its process plan be generated automatically within a few minutes. Current results show that the system is reliable for a workpiece which has clearly defined features.

CAD/CAM

Conclusion

been reached where it is imperative to adopt these techniques to remain competitive. As the application of C A D on the one hand and CAM modules such as CAPP, NC, DNC, FMS, and AGVs on the other hand has become more widespread, the need to integrate these systems has become apparent. Although current

Advances in technology have made it viable for computers to be used more widely in a variety of

Vol 6 N o 4 N o v e m b e r 1993

applications

including

manufacturing

technology.

systems are now becoming firmly estab-

l i s h e d in m a n u f a c t u r i n g i n d u s t r y , a n d a s t a g e h a s n o w

241

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ICAPP: A process planning sys~mforthe CIMenvironment

COMPACT II MACIIIN,L63 IDDIX,, D~IO Oil H/O

20 IIilT,I~TEIC 8ElllP, O.OOX, O.OOl, 40.OOZ BASle, 20.00XA, 20.OOYA, 20.00ZA DPT 1, 6.O00XB, 6.000T8, O.O00ZB DPT 2, 6.~OXD, 46.O00YB, O.~OZD DLIl I,PT I,PT 2 OPT 3, 66.00018, 6.O00TB, O.O00ZB DPT 4. EE.OOOXD. 46.O00TB, O.O00ZO DLIl 2,PT 3.PT 4 DPT 6, 47.600XB, 30.000Y0, O.O00ZB DPT 0. 12.600XB, 30.O00TB, O.O00ZD DSET I,RPT 6,8(PT 6),F(PT 6), 3EQSP,IIONOR£ DPT 7, 12.600XB, $O.O00TB, O,O00ZB DPT 8. 12.500XD, 31.O00YÚ. O.O00ZD DPT 0, 12.600XB, 19.O00Te, O.O00ZB DSET 2,1UPT O,B(PT 8),F(PT 0), 3EQSP,flOMOR£ DPT tO, 12.600XD, IV.OOOTB. O.O00ZB DPT 12, JO.600XB, 18.O00TB, O.O00Z8 DPT 13, 10.500XB, $2.OOOTB, O.O00ZD DLIZ 3,PT 12.PT 13 DPT 14, 43.600XB, 18.0DOTE, O.O00ZB DLfl 4,PT 2.PT 14 DPT 15, 43.60019, 32,00OLD, O.O00ZD DLN 6,PT 4,PT 15 DLN 6,PT 6.PT 3 DLr¿ ?,PT 3,PT 2 DPB I,RPT.PT II;SPT,PT I;CL,CONV ;5(LN 3),L~ 4 ;L, 6 ;LN e ;LN 7 ;F(LN 4),nOMORE DPT 10, 4.600XB, 26.000Y9, O.O00ZB DPT 17, 66.600XB, 26.O00YB, O.O00ZB ATCHO,TOOL 1,00L, 125.00TD MOVE, PTI6 CUT. 17g.~4 14,~N, PTl7 ATCHO,TOOL 2,0GL, 4.00TD CUT. EIITRTC 1.2 ZB, PLUIlOE), CLIHB, - 10.000 ZB, ;OVRLAP .OI,1362.340MMPM,L362.34gP.P~I, POCKET 1 ATCHG.TOOL 3,0GL, 3.00TD,118TPA, O.13h~lPR,2726 4RPM DRL,SET 1,PT 7, 6.O00DP DRL.SET 2.PT 10. 6.O00DP HO~IE EIJD

APT PARTflO DEMO CI.PEIIT HAOllZillHPgllCg, 0 0.000, 40.000 IITPT-POIOTI O. 000. 20.000, 20.000 Ki11uEr-HATEIX / I?.AIlSL, 20.000, EE/1TB/MATIt~ 6.000, 0.000 PT I'PO 11111 6.000, 48.000, 0.000 PT 2,'1)0III1/ 6. 000, LiT IsLXIIE/ PT 1, PT 3 6.000, 0.000 PT 3mPOlilT/ 66.000, 46.000, 0.000 PT 4tPOlilTI $6.000. Lil 2-LIllE/ PT 3, PT 4 36.000, -3.260 PT 6~POINT/ 4'/. 600, $e.O00, -3.260 PI' O-POlliT/ 12. 600, PAX I-PATFJtii/LIIlUE, PT S, PT e, 3 31.000, -3.250 PT 8,,POZilT/ 12.600, 19.000, -3.260 PT 9-POX/iT/ 12. 600, PAT 2-PITEIUI/LXIIEAIL, PT 8. PT 9, 3 18.000, 0.000 PT 12-POIIlT/ 16.600, le.600, 32.000, 0.000 PT 13-POXflT/ 18.000, 0.000 PT 14-POlilTI 43.600, 32.000, 0.000 PT I6-PO I I I T i 43.600, 4.600, 26.000, 0.000 PT 10-POIrlT/ 86.600, 26.000, 0.000 PT 17-POlill/ TOOL IlO/ 1 LOADYL/ 1 CUTTER/ 136.000 FROHISTPT FEDRAT/ITg.44 SPIODL/IeO. OO OOTO/ PT I0 OOT0/ PT 17 GOTO/STPT TOOL nO/ 2 LOADTL/ 2 C'dTTER/ 4.000 FP.,OM/STPT 5"PIIIDL/ 1363. O0 13.000 PL 1-PLlflE/O,O, 1, -

PSIS/PL 1 POCKET/ 2.000, 2111.16,

0.000,

1.000,

1.000,

261.16,8

O, 3,$

PT12 .PT 135 .PT 165

,PT 14 TOOL !i0/ 3 LOADTL/ 3 COTTF-q/ 3.00o

FROI4/STPT FEDRAT/ O. 13 SPIflDL/ 2726. O0 CYCLE/DRILL. 6.26 GOTO/PAY 1 GOTO/PAT 2

CTCLE/flOHORE a0TO/STPT FIJSI

Figure 4. Part programs generated by the system

research is concentrating on the transfer of geometry and design information to CAPP systems, is also important to develop the interface between CAPP and the various C A M modules. A system has been developed for prismatic parts, which takes full advantage of the process planning features of the program and can

242

generate working part programs. The system has proved its versatility in handling both A P T and C O M P A C T II. The purpose of this work was to link process planning with both design and manufacturing. This has been achieved by feeding the required geometry data

Computer Integrated Manufacturing Systems

M E SSEMAKULA from a CAD system into a process planning system, using the IGES geometry data representation scheme. The approach is general enough that any CAD system generating standard IGES files can serve as the front end. The input IGES file is processed to extract the desired geometry data in a form suitable for use within the ICAPP process planning system. The system was tested using a selection of simple features such as holes, slots and pockets. It has been shown that the extracted geometry data can be used directly by the ICAPP system to automatically generate detailed process plans as well as NC part programs.

References

1 Weili, R, Spur, G and Eversheim, W 'Survey of computer aided process planning systems', Ann. CIRP, Vol 31 No 2 (1982) pp 539-551 2 Halevi, G The Role of Computers in Manufacturing Processes, Wiley, New York (1980) 3 Chang, T C and Wysk, R An Introduction to Automated Process Planning Systems, Prentice Hall, Englwood Cliffs, NJ (1985) 4 Harhalakis, G, Marks, L and Bohse, M 'Integration of manufacturing resource planning (MRP II) systems with computer aided design (CAD)', Proc. 13th Conf. NSF Production Res. Technol. Program, University of Florida, USA (November 18-21 1986) 5 Lesko, J 'MIPLAN, implementation at Union Switch & Signal', CAPP Computer Aided Process Planning, Computer and Automated Systems Association of SME (1985) pp 57-63 6 Schwartz, S J and Shreve, Mt 'GT and CAPP Productivity tools for hybrids', Int. J. Hybrid Microelectronics, Vol 5 No 2 (November 1982). 7 Evershiem, W and Esch, H 'Automated generation of process plans for prismatic parts', Ann. CIRP, Vol 32 No 1 (1983) pp 361-364 8 Wysk, R A An Automated Process Planning and Selection Program: APPAS, PhD Thesis, Purdue University, USA (1977) 9 Nau, D S and Chang, T C 'A knowledge based approach to generative process planning', Computers and Intelligent Process Planning: Winter Annual

Vol 6 No 4 November 1993

Meeting of ASME, Florida, USA (November 17-22 1985) pp 69-71 10 Harvey, R 'CAPP: Critical to CAD/CAM success', Iron Age (September 23 1983) 11 Eversheim, W and Holz, B 'Computer aided programming of NC-machine tools by using the system AUTAP-NC', Ann. CIRP, Vol 31 No 1 (1982) pp 323-327 12 Kramer, T and Jun, J 'Software for an automated machining workstation', Proc. Int. Machine Tool Technical Conf., Chicago, IL (September 1986) 13 Eskicioglu, H and Davies, B J 'An interactive process planning system for prismatic parts (ICAPP)', Ann. CIRP, Vo132 No 1 (1983) pp 365-370 14 Ssemakula, M E and Davies, B J 'Integrated process planning and NC programming for prismatic parts', Proc. 1st Int. Machine Tool Conf., Birmingham, UK (June 26-28 1984) pp 143-154 15 Initial Graphics Exchange Specification (IGES) Version 4.0, US Department of Commerce, National Institute of Standards and Technology, Gaithersburg, MD (1988) 16 Report on S E T - Standard for Exchange and Transfer, AFNOR Standard 68-300, release 85-08 (1985) 17 Workstation Alert, Vol 1 No 4 (1984) 18 Ssemakula, M E, and Satsangi, A 'Application of PDES to CAD/CAPP integration', Comput. & Ind. Eng., Vol 18 No 4 (1990) pp 435-444 19 Ssemakula, M and Rangachar, R 'The prospect of process sequence optimization in CAPP systems', Comput. & Ind. Eng., Vo116No 1 (1989) pp 161-170 20 Park, M W and Davies, B J 'Integration of process planning into CAD using IGES', Proc. 19th CIRP Seminar on Manuf. Syst., Pennsylvania State University, PA (June 1-2 1987) pp 315-317 21 Wang, H and Wysk, R 'Turbo-CAPP: A knowledgebased computer aided process planning system', 19th CIRP Seminar on Manuf. Syst., Penn State University (June l-2 1987) pp 161-167 22 Santochi, M and Giusti, F 'Proposal of a product modeler oriented to manufacturing problems', 19th CIRP Seminar on Manuf. Syst., Penn State University (June 1-2 1987) pp 27-31 23 Ssemakula, M E and Gill, J S 'CAD/CAPP integration using IGES', Advanced Manuf. Eng., Vol 1 No 5 (1989) pp 264-270

243